Paris Hilton should return up to $1 million she was paid for the 2006 box-office bomb "Pledge This!" because she didn't plug the film enough, an attorney for the movie's investors told a federal judge Thursday.

The 29-year-old hotel heiress, actress and self-promoting businesswoman refused nine requests for print and broadcast interviews she should have given under her contract, said investor attorney Bryan West.

"We paid her $1 million, and we're entitled to get at least a portion of that back," West told U.S. District Judge Federico Moreno. "Part of what actors do is promote their films."

But Hilton's attorney, Michael Weinsten, said she took part in several high-profile publicity events - including an appearance at the Cannes Film Festival - and that the contract didn't require her to do interviews when she was busy on other projects.

Weinsten added that Hilton also had the right to approve or reject any proposals or offers.

"Paris Hilton is a brand. That is her value, and how she makes money," he said. "She did substantial publicity."

Hilton, who testified last summer at a trial over the dispute, did not attend Thursday's hearing. She said previously that although dissatisfied with the finished "Pledge This!" cut, she wanted the college sorority romp to succeed and worked hard to make that happen. Yet the film only made $2.9 million.

Moreno previously rejected the investors' effort to sue Hilton for $8.3 million in damages, which included the $1 million she was paid for her acting and as executive producer. But he left open the possibility that she might have to repay some or all of that fee as restitution if she did not fulfill her publicity obligations.

Moreno did not indicate when he would rule. The case centers on determining the value of the appearances Hilton did against the cost of those she rejected, which ranged from a proposed appearance on NBC's "Tonight Show" to phone chats with several British publications.

"The question is, what is the value of what she did do? Because she did do something," Moreno said. "How do I quantify it?"

Hilton was sued by attorney Michael Goldberg, a court-appointed receiver for a now-defunct entertainment company that was the major investor in "Pledge This!" The company, Worldwide Entertainment Group, was shut down as a suspected $300-million Ponzi scheme by the Securities and Exchange Commission, and Goldberg is attempting to recoup losses for some 3,300 investors in the company.

Both sides acknowledge Hilton's ability to move a product. Goldberg said Thursday that sales of the "Pledge This!" DVD spiked last summer amid publicity surrounding the trial, although he did not provide exact sales numbers.